Audi a4 b6 1.9 tdi 96 kw 2003 - hums at a certain engine RPM

[ciki022]

Hallo,
I've had the car for a few years, and recently it started making an unpleasant humming sound, only at a certain engine RPM, for example in 3rd or 4th gear under medium throttle. Nothing shakes, just that humming sound, which stops immediately when you step on the throttle. The car was taken to a mechanic, and the cause was not discovered (the engine runs fine, all the engine mounts were checked, the exhaust was not wobbling or getting caught somewhere). The right engine mount was replaced 2 years ago, and the left one with the sensor 3 months ago, the engine mount on the transmission is good, there is no rattling when you step on the throttle. It is mentioned that the floating flywheel can also be a problem, it is good, it doesn't shake at idle, it doesn't vibrate when starting and stopping. If you have any ideas, I would be very grateful.

[Stevey Y]

32 minutes ago, ciki022 said:

Hallo,
I've had the car for a few years, and recently it started making an unpleasant humming sound, only at a certain engine RPM, for example in 3rd or 4th gear under medium throttle. Nothing shakes, just that humming sound, which stops immediately when you step on the throttle. The car was taken to a mechanic, and the cause was not discovered (the engine runs fine, all the engine mounts were checked, the exhaust was not wobbling or getting caught somewhere). The right engine mount was replaced 2 years ago, and the left one with the sensor 3 months ago, the engine mount on the transmission is good, there is no rattling when you step on the throttle. It is mentioned that the floating flywheel can also be a problem, it is good, it doesn't shake at idle, it doesn't vibrate when starting and stopping. If you have any ideas, I would be very grateful.

Hi it might be the front crank pulley as with age the rubber bonding on the pulley deteriorates and can be noisy at certain rpm, if the noise is at between 1800 and 2000 rpm its probably the rubber on the pulley going bad.

Steve.